1. Field of the Invention
This invention relates to a floss separating apparatus which is used in pipelines conveying particles such as chemical raw materials with the aid of gas. The apparatus separates floss materials (such as tape-shaped films or powder) from the particles.
2. Background of the Invention
In general, in conveying particles of synthetic resin such as polyethylene with the aid of air, the particles may become molten and stuck to the inner wall of a conveying pipe by frictional heat. The particles thus stuck are peeled off from the pipe wall, thus forming small pieces of film. If the pipe wall is uneven, the particles are worn into powder during the transport of particles. The pieces of film peeled off from the pipe wall or the powder thus formed lower the quality of the resultant product. In addition, sometimes the pieces of film and the powder are mixed together, thus forming pill-shaped balls which make it difficult to discharge the particles through the hopper. Depending on the method of use, the powder may cause public hazards. Therefore, it is necessary to separate the pieces of film and the powder (hereinafter referred to as "floss materials" or merely as "floss,") from the particles during the conveyance. An apparatus for satisfying this requirement has been proposed by Japanese Utility Model Application Publication No. 6432/1980.
In the conventional apparatus, the stream of particles are conveyed downwardly with the aid of air. A floss separating air stream is jetted horizontally to the stream of air-carried particles to thereby move the floss materials sidewards to remove them from the stream of particles. In the conventional apparatus, the floss materials are separated from the particles by utilization of the difference between the floating velocity of particles falling freely and the floating velocity of the floss materials. That is, the velocity of the air curtain is set to a value higher than the floating velocity of floss and much lower than the floating velocity of particles. Therefore, in separating a substance that has a small difference in the floating velocity from the particles, the separation efficiency is low. The pieces of tape-shaped film, being floated in the floss separating section, are liable to form pill-shaped balls. The balls thus formed increase in weight and may clog the fluid discharging outlet, which lowers the separation efficiency.
Another example of the floss separating apparatus has been disclosed by Japanese Patent Application (OPI) No. 133878/1983 (the term "OPI" is used herein meaning "an unexamined published application"). In the apparatus, particles are conveyed downwardly with the aid of air, while a floss separating air stream is jetted into the stream of particles upwards, thereby to remove floss from the stream of particles. In the apparatus, in order to improve the efficiency of a floss separating in which particles are allowed to freely fall down, the particles are conveyed by a stream of gas, and the difference between the velocity of the particles and the velocity of the secondary gas is utilized. However, in the apparatus, the classification and the separation are carried out at the same place, and therefore the floss materials separated may be mixed into the particles which fall continuously. That is, the apparatus is also disadvantageous in that the separation efficiency is low.
Thus, it is difficult for these conventional apparatuses to sufficiently separate the floss from the particles.
In addition, floss separating apparatuses have been disclosed by Japanese patent application Publication No. 16626/1979, Japanese patent application (OPI) No. 80063/1976, Japanese patent application Publication No. 11264/1983 and Japanese Utility Model Application Publication No. 25096/1979. However, similarly as in the above-described conventional apparatus, these floss separating apparatuses are also disadvantageous in that the floss cannot be sufficiently removed from the particles.
This invention is intended to increase the floss separation efficiency in a floss separating system or apparatus utilized for a system of conveying particles with the aid of gas stream.
In the invention, secondary and tertiary gas streams are utilized for separation of floss. That is, in a floss separating apparatus of the invention, a hopper with a closed structure having a cylindrical wall is arranged in such a manner that the hopper extends vertically. A pipe-shaped structure is arranged inside the hopper in such a manner that the pipe-shaped structure extends vertically and is coaxial with the hopper so that an annular passageway space is formed between the hopper wall and the pipe-shaped structure. The passageway space provides a particle flow down section. A floss separating section and a particle discharging passageway are arranged in the stated order from above. A space above the upper end of the hopper is utilized to form a particle scattering section. The outlet of a particle conveying passageway for conveying particles with primary gas opens into the central portion of the particle scattering section. A striking plate is provided at a position where the striking plate confronts the outlet of the particle conveying passageway. The upper end of the particle flow down section opens into the periphery of the particle scattering section. A partition wall structure is provided in such a manner that the partition wall structure surrounds the particle discharging passageway. A floss discharging annular floss passageway is provided around the partition wall structure. The upper end of the floss passageway opens into the periphery of the floss separating section. A secondary gas passageway is formed inside the pipe-shaped structure. A plurality of secondary gas jetting outlets are formed in the part of the pipe-shaped structure which is surrounded by the floss separating section in such a manner that the secondary gas jetting outlets are distributed all around the pipe-shaped structure. The partition wall structure is hollow, thus providing a tertiary gas chamber. A plurality of tertiary gas jetting outlets are formed in the partition wall of the partition wall structure which is located between the tertiary gas chamber and the particle discharging passageway in such a manner that the tertiary gas jetting outlets are distributed all around the partition wall and the lower outlet of the particle discharging passageway is connected to a particle discharging mechanism which can discharge particles while substantially interrupting the flow of gas.
In one embodiment of the invention, the above-described pipe-shaped structure is a dual-pipe structure having an outer wall and an inner wall, the particle conveying passageway is formed inside the inner pipe. The upper end opening of the inner pipe forms the outlet of the particle conveying passageway. The second gas passageway is provided by the annular space between the outer pipe and the inner pipe of the pipe-shaped structure.
Particles with floss materials are conveyed in the particle conveying passageway with the aid of the primary gas stream into the particle scattering section.
The particles, striking against the striking plate, are uniformly scattered towards the periphery of the particle scattering section and are delivered to the upper end of the particle flow down section.
The particles flow down the particle flow down section while being uniformly scattered therein. While flowing down the particle flow down section in this manner, the particle flow is rectified and forms, cylindrical film stream (the velocity being about 10 to 30 m/s), and the cylindrical stream of particles runs into the floss separating section.
In the floss separating section, as shown in FIG. 4, the secondary gas streams are jetted at high velocity (80 to 250 m/s) from the number of secondary gas jetting outlets formed in the outer pipe of the pipe-shaped structure in the region immediately below the particle flow down section in such a manner that the secondary gas streams go across the cylindrical stream of particles, while the tertiary gas streams are blown up the pipe-shaped structure from the particle discharging passageway at a velocity (3 to 7 m/s) lower than the floating speed of the particles.
The heavy particles introduced into the floss separating section have been accelerated and have an inertia imparted thereto. Therefore, the particles pass through the secondary gas streams running horizontally and the tertiary gas streams moving upwardly, and flow into the particle discharging passageway.
On the other hand, the floss materials have small inertia (being small in mass). Therefore, upon arrival at the floss separating section, the floss materials are blown outwards by the secondary gas streams jetted radially outwardly at high velocity. As a result, the floss materials are caused to flow on the outward composite stream of the primary, secondary and tertiary gas streams into the floss passageway.
The floss materials delivered into the floss passageway are discharged therefrom, while the particles delivered into the particle discharging passageway are discharged through the particle discharging mechanism.
The particle discharging mechanism can substantially interrupt the flow of gas. That is, the particle discharging mechanism can prevent the flow of secondary or tertiary gas through it. Accordingly, the secondary gas streams flowing radially outwardly and the tertiary gas streams upwardly can be positively formed as was described above.